(1) Field of the Invention
The present invention relates to a near infrared absorbent polycarbonate resin composition and a shaped article thereof. More particularly, the present invention relates to a near infrared absorbent polycarbonate resin composition using a diimmonium type near infra red absorber, wherein the thermal stability of the diimmonium type near infra red absorber is improved so as to allow its long-term use even at high temperatures; as well as to a shaped article made of the resin composition.
(2) Description of the Prior Art
In recent years, infrared or near infrared absorption filters have found wider applications.
As the material for such infrared or near infrared absorption filters, there have heretofore been used a glass containing metal oxides such as ferric oxide, copper oxide etc., or a glass which surface is coated with a thin layer or layers of a metal or metal oxide. Recently, however, there has come to be used a shaped article of a resin composition comprising an easily shapeable lightweight transparent resin and a near infrared absorber.
Infrared or near infrared absorbent glass filters mentioned as above, however, are inconvenient to handle, since thye are heavy and crack easily. Also they are difficult to process by, for example, bending or punching.
Also, infrared or near infrared absorbent filters made of a resin composition comprising a transparent resin and a near infrared absorber are low in reliability in long-term use and, when used for a long period of time under severe conditions (e.g. high temperature and high humidity) come to show changed absorbing wavelength range because of degradation or decomposition of the near infrared absorber.
Of near infrared absorbers, on the other hand, diimmonium type near infrared absorbers show almost no absorption in a visible region, but wide range of absorption in near infrared and infrared region, which satisfy the requirements for infrared or near infrared absorbent filter. Meanwhile, the diimmonium type near infrared absorbers are known to be unstable to heat and have had various problems to be solved.
The present inventors made a study on the stability of diimmonium type near infrared absorbers in various resins, and found out that their stability particularly in polycarbonate resin are very high as compared with the stability in other resins. The present inventors made a further study and completed the present invention.